Overview
SS-31 (D-Arg-Dmt-Lys-Phe-NH2), also known as elamipretide or Bendavia, is a synthetic cell-permeable tetrapeptide that selectively concentrates in mitochondrial inner membranes, where it binds to cardiolipin—a phospholipid unique to mitochondria that is essential for electron transport chain (ETC) function. Developed by Stealth BioTherapeutics, SS-31 is the most clinically advanced mitochondria-targeted peptide, with multiple completed phase II and phase III clinical trials.
Mitochondrial dysfunction is increasingly recognized as a central driver of aging, heart failure, neurodegenerative disease, and metabolic disorders. As organisms age, cardiolipin becomes oxidized and structurally altered, impairing the efficiency of the electron transport chain and increasing production of reactive oxygen species (ROS). SS-31 stabilizes cardiolipin-cytochrome c interactions, restoring ETC efficiency and reducing mitochondrial ROS production.
Clinical trials have evaluated SS-31 for Barth syndrome (a genetic cardiolipin deficiency), primary mitochondrial myopathy, heart failure with reduced ejection fraction, and age-related mitochondrial dysfunction. Results have been mixed—with clear biomarker improvements but variable clinical endpoint outcomes—highlighting the complexity of translating mitochondrial improvements to clinical benefits.
This guide reviews SS-31's unique mitochondria-targeting mechanism, clinical trial data, safety profile, and its significance within the broader field of mitochondrial medicine and longevity research.
Quick facts
- Mechanism
- Cardiolipin-stabilizing tetrapeptide restoring mitochondrial ETC efficiency
- Primary use
- Mitochondrial Function & Cellular Energy
- Evidence
- moderate
- FDA
- Not approved
- Route
- Subcutaneous injection or intravenous infusion
- Typical results
- Improved mitochondrial function and exercise capacity in clinical trials
Chemical information
SS-31 (C₃₂H₄₉N₉O₅) is a longevity compound with a molecular weight of 639.8 g/mol. Its structural characteristics underpin its biological activity in longevity and anti-aging research.
How SS-31 works
SS-31 concentrates more than 5,000-fold in mitochondrial inner membranes within minutes of cellular uptake, driven by the electrochemical gradient across the mitochondrial membrane. Once localized, it binds selectively to cardiolipin through electrostatic and hydrophobic interactions. This binding stabilizes the cardiolipin-cytochrome c complex, which is essential for efficient electron transfer between Complex III and Complex IV of the ETC.
Cardiolipin is a unique dimeric phospholipid found exclusively in mitochondrial inner membranes, where it constitutes approximately 20% of the lipid content. It serves structural and functional roles: anchoring ETC complexes, facilitating supercomplex formation, and directly participating in cytochrome c binding. With aging, cardiolipin is progressively oxidized by mitochondrial ROS, leading to ETC dysfunction, increased electron leak, and a vicious cycle of further ROS production and cardiolipin damage.
SS-31 breaks this vicious cycle by stabilizing the interaction between cardiolipin and cytochrome c, preventing cytochrome c from adopting its peroxidase conformation that catalyzes cardiolipin oxidation. This protection maintains efficient electron flow through the ETC, reduces superoxide production at Complex I and Complex III, and preserves mitochondrial membrane potential—the driving force for ATP synthesis.
Beyond ETC protection, SS-31 has been shown to restore mitochondrial dynamics (fusion-fission balance), improve mitophagy (selective removal of damaged mitochondria), and reduce mitochondrial permeability transition pore opening—a key event in apoptotic cell death. These comprehensive effects on mitochondrial quality control make SS-31 a broad-spectrum mitochondrial protective agent.
- Cardiolipin binding: Selectively binds cardiolipin in mitochondrial inner membranes to stabilize ETC function
- 5,000-fold concentration: Accumulates in mitochondria driven by electrochemical gradient
- Cytochrome c stabilization: Prevents cardiolipin-cytochrome c dissociation and peroxidase activity
- ROS reduction: Reduces electron leak at Complex I and III without acting as a direct antioxidant
- ATP restoration: Improves coupling efficiency to restore ATP synthesis capacity
- Mitochondrial dynamics: Normalizes fusion-fission balance and enhances mitophagy
Pharmacokinetics
| Parameter | Value | Significance |
|---|---|---|
| Bioavailability (SC) | ~100% | Complete absorption from subcutaneous injection |
| Mitochondrial concentration | >5,000-fold | Extreme concentration in target organelle |
| Half-life | ~4 hours (plasma) | Effects persist beyond plasma clearance due to mitochondrial retention |
| Tmax (SC) | ~1 hour | Rapid absorption and mitochondrial targeting |
| Cell uptake | Energy-independent | Crosses membranes without requiring active transport |
| Molecular weight | 639.8 g/mol | Small tetrapeptide with excellent cell permeability |
Dosing & administration
SS-31 dosing varies by indication and individual factors. No FDA-approved dosing exists for this compound; protocols in the literature derive from limited clinical or preclinical data and practitioner experience.
Any use should be conducted under qualified medical supervision with appropriate monitoring of safety markers.
Important: These dosing ranges are not FDA-approved. Any use should be under qualified medical supervision.
Side effects & safety
Safety data for SS-31 is primarily derived from preclinical studies and limited human data. Long-term effects in humans remain incompletely characterized.
Common
- • Injection site reactions (most common in clinical trials)
- • Headache
- • Nausea
- • Fatigue (typically transient)
- • Dizziness
Serious / potential risks
- • Generally well-tolerated in clinical trials
- • Rare infusion reactions with IV administration
- • No dose-limiting toxicities identified in phase I/II trials
- • Long-term safety data still accumulating
Drug interactions
| Medication | Interaction | Recommendation |
|---|---|---|
| CoQ10 / Ubiquinol | Both target ETC function; potentially synergistic | Commonly combined in mitochondrial support protocols |
| Metformin | Metformin inhibits Complex I; SS-31 may partially counteract this | Monitor for altered metformin efficacy; potential complementary use |
| Statins | Statins can impair CoQ10 synthesis and mitochondrial function | SS-31 may help mitigate statin-related mitochondrial effects |
| NAD+ precursors (NMN/NR) | Both support mitochondrial function through different mechanisms | Potentially synergistic; commonly combined in longevity protocols |
Storage & handling
Lyophilized (powder)
- • Store at -20°C to 4°C (freezer or refrigerator)
- • Protect from light and moisture
- • Stable for 12–24 months when stored properly
- • Keep in original sealed container until reconstitution
Reconstituted solution
- • Refrigerate at 2–8°C after reconstitution
- • Use bacteriostatic water for multi-dose reconstitution
- • Typical stability: 14–28 days refrigerated
- • Do not freeze reconstituted solution
Cost & availability
| Source | Cost | Notes |
|---|---|---|
| Research peptide suppliers | $60–$120 per 5mg vial | Custom synthesis required; verify purity |
| Clinical trials | N/A (investigational) | Available through clinical trial enrollment where applicable |
| Compounding pharmacies | $200–$400 per month | Limited availability; prescription required |
The bottom line
SS-31 is the most clinically advanced mitochondria-targeted peptide, with demonstrated ability to restore electron transport chain efficiency by stabilizing cardiolipin. Clinical trial results have shown biomarker improvements in mitochondrial function, though translation to robust clinical endpoints has been variable. It represents a promising approach to addressing the mitochondrial dysfunction that underlies aging and multiple diseases.
Best for
- • Researchers studying mitochondrial dysfunction in aging and disease
- • Clinical trials in mitochondrial myopathy and heart failure
- • Longevity-focused protocols targeting cellular energy restoration
- • Individuals with documented mitochondrial dysfunction under specialist care
Not for
- • Self-treatment without specialist supervision
- • Those expecting rapid symptomatic improvement
- • Replacement for foundational health practices (exercise, nutrition, sleep)
- • Individuals without documented mitochondrial pathology
Related compounds
Frequently asked questions
References
- [1] Szeto HH.. First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics. Br J Pharmacol (2014). doi: 10.1111/bph.12461 PMID: 24116661
- [2] Birk AV, Liu S, Soong Y, et al.. The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin. J Am Soc Nephrol (2013). doi: 10.1681/ASN.2012121216 PMID: 23687356
- [3] Siegel MP, Kruse SE, Percival JM, et al.. Mitochondrial-targeted peptide rapidly improves mitochondrial energetics and skeletal muscle performance in aged mice. Aging Cell (2013). doi: 10.1111/acel.12102 PMID: 23834033
- [4] Reid Thompson W, Hornby B, Manuel R, et al.. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate the effectiveness of elamipretide in Barth syndrome. Genet Med (2021). doi: 10.1038/s41436-020-01006-8 PMID: 33087895
- [5] Szeto HH, Birk AV.. Serendipity and the discovery of novel compounds that restore mitochondrial plasticity. Clin Pharmacol Ther (2014). doi: 10.1038/clpt.2014.174 PMID: 25188727